A Pre-Shaped MMI Input Structure in Etched Diffraction Grating for Flat-Top Spectral Response with Low Crosstalk
低串扰平顶型刻蚀衍射光栅解复用器的设计

A flat-topped planar waveguide demultiplexer with low crosstalk is designed.A multimode interference (MMI) section with a reshaping taper is connected at the end of the input waveguide.An etched diffraction grating (EDG) demultiplexer is considered as a design example.A wide-angle beam propagation method (BPM),the Kirchhoff diffraction theory,and the mode propagation analysis are used in the simulation.The field distribution at the end of the taper is reshaped optimally to have sharp transitions.The designed EDG demultiplexer has an excellent flat-topped spectral response and a very low crosstalk,and a low chromatic dispersion characteristic.